Method for preparing polyether copolymers with polycarbonates and polyarylates

ABSTRACT

Copolymers of polycarbonates or polyarylates with polyether polymers such as polyethersulfones, polyetherketones, and polyetherimides are prepared by reaction of the polyether polymer-forming reagents, e.g., bisphenol A disodium salt and bis(4-chlorophenyl)sulfone, in the presence of the polycarbonate or polyarylate. The reaction may take place in a dipolar aprotic solvent, or in a water-immiscible aromatic solvent in the presence of a phase transfer catalyst, preferably a hexaalkylguanidinium halide. Hydroxy-terminated polyether oligomers may be produced from the copolymers by saponification of carbonate or ester groups.

BACKGROUND OF THE INVENTION

This invention relates to condensation copolymer preparation, and moreparticularly to the preparation of copolymers of polyether polymers andoxycarbonyl group-containing polymers.

Polycarbonates, polyarylates, polyethersulfones, polyetherketones, andpolyetherimides (the latter three frequently being collectivelydesignated “polyether polymers” herein) are known high performancepolymers characterized by various desirable properties. It is frequentlyof interest to combine these properties. Combined properties can oftenbe attained by forming blends of two polymers. However, polycarbonatesand polyarylates are typically incompatible with most polyetherpolymers, forming poorly dispersed blends which may be opaque andunsatisfactory for such applications as glazing and fabrication ofoptical disks.

Therefore, the preparation of copolymers containing both ether-derivedand carbonate or ester structural units is of interest. Methods forpreparation of such copolymers are hard to develop, since thepreparation methods characteristic of each type of polymer are widelydifferent. Polycarbonates are conventionally produced from bisphenolseither by reaction with phosgene in a two-phase organic-aqueous systemunder basic conditions or by reaction with diphenyl carbonate in themelt, and polyarylates are produced under similar conditions. Polyetherpolymers, on the other hand, are frequently produced by reaction betweena salt of a dihydroxyaromatic compound and a dihaloaromatic compoundunder anhydrous conditions in a dipolar aprotic solvent or awater-immiscible aromatic solvent of low polarity. None of these methodsof preparation can be used for both polycarbonates or polyarylates andpolyether polymers.

A method of copolymer preparation has been described by McGrath et al.(Polymer Engineering Science, vol. 17, pp. 647-651, 1977) in whichhydroxy-terminated polyethersulfone oligomers are first synthesized in adipolar aprotic solvent. Said oligomers are then isolated and employedin an interfacial reaction with a monomer such as bisphenol A, in ahalogenated solvent such as methylene chloride. This synthesis requirestwo successive, different polymerization reactions under widelydifferent conditions and is thus cumbersome.

It would be more practical to conduct both steps, i.e., the preparationof the polyether oligomers and their reaction to form polycarbonate orpolyarylate copolymers, in a single solvent. In addition, low to mediummolecular weight hydroxy-terminated polyether oligomers are useful tomake short-block, random, block copolymers, which do not exhibit complexmulti-phase morphology often observed for long-sequence blockcopolymers.

Copolymer and oligomer preparation has not been readily achievable,however, by reason of differences in solubility between an alkali metalsalt of the dihydroxyaromatic compound and the dihaloaromatic compound,as illustrated by bis(4-chlorophenyl)sulfone. In a homogeneous solutionpolymerization, such as the procedure in dipolar aprotic solvents,hydroxy-terminated polyether oligomers with statistically distributedmolecular weight can be readily prepared simply by use of an excess ofthe dihydroxyaromatic compound. However, it is not possible to make sucholigomers of low to moderate molecular weights in non-polar solvents,even when phase transfer catalysts are employed. This is true becausethe alkali metal (e.g., sodium) salt of the dihydroxyaromatic compoundis typically insoluble in relatively non-polar solvents such as anisoleand dichlorobenzene. In the presence of phase transfer catalyst, aminute amount of the salt may be solubilized at any moment. As thesolubilized salt reacts with the dihaloaromatic compound in solution,more salt dissolves to maintain its minute steady state concentration.At the end of the reaction, when all the dihaloaromatic compound isconsumed, the excess salt is left undissolved without participating thepolymerization reaction. Thus, despite use of excess dihydroxyaromaticcompound the system behaves like an equimolar polymerization, resultingin high molecular weight polymer.

It is of interest, therefore, to develop a simple method for thesynthesis of highly random polyether-polycarbonate andpolyether-polyester copolymers. It is also of interest to develop amethod for preparing and isolating low to medium molecular weighthydroxy-terminated oligomers of the polyether polymers, rather thanproducing only high molecular weight polymers.

SUMMARY OF THE INVENTION

The present invention is based in part on the discovery that whenpolyether polymers are prepared in relatively non-polar solvents in thepresence of polycarbonate or a polyarylate, extensive exchange takesplace with incorporation of carbonate or arylate units in the productpolymer in relatively random fashion.

The invention in one of its aspects, therefore, is a method forpreparing a copolymer of a first polymer which is a polyethersulfone,polyetherketone, or polyetherimide and a second condensation polymercharacterized by structural units containing an oxycarbonyl group, whichcomprises contacting, under reactive conditions, at least one salt of adihydroxyaromatic compound with at least one substituted aromaticcompound of the formula

Z(A¹—X¹)₂,  (I)

wherein Z is an activating radical, A¹ is an aromatic radical and X¹ isfluoro, chloro, bromo or nitro, in the presence of said second polymer.

It has further been discovered that the product copolymers can bedegraded by saponification into hydroxy-terminated oligomers of thepolyether polymers. Said oligomers are capable of conversion intospecial purpose copolymers, such as optical grade copolyethercarbonates,by means of an interfacial polymerization in the same vessel or byaddition to a melt polycarbonate preparation mixture.

Another aspect of the invention, therefore, is a method for preparing atleast one hydroxy-terminated oligomer of a polyether polymer whichcomprises preparing a copolymer as described above and contacting saidcopolymer with alkali metal hydroxide under reactive conditions, thushydrolyzing carbonate and ester units.

DETAILED DESCRIPTION; PREFERRED EMBODIMENTS

The alkali metal salts of dihydroxy-substituted aromatic hydrocarbons(hereinafter sometimes designated simply “salt” for brevity) which areemployed in the present invention are typically sodium and potassiumsalts. Sodium salts are frequently preferred by reason of theiravailability and relatively low cost. Said salt may be employed inanhydrous form. However, in certain instances the employment of ahydrate, such as the hexahydrate of the bisphenol A disodium salt, maybe advantageous provided water of hydration is removed before thesubstituted aromatic compound is introduced.

Suitable dihydroxy-substituted aromatic hydrocarbons include thosehaving the formula

HO—A²—OH,  (II)

wherein A² is a divalent aromatic hydrocarbon radical. Suitable A²radicals include m-phenylene, p-phenylene, 4,4′-biphenylene,4,4′-bi(3,5-dimethyl)phenylene, 2,2-bis(4-phenylene)propane and similarradicals such as those which correspond to the dihydroxy-substitutedaromatic hydrocarbons disclosed by name or formula (generic or specific)in U.S. Pat. No. 4,217,438.

The A² radical preferably has the formula

—A³—Y—A⁴—,  (III)

wherein each of A³ and A⁴ is a monocyclic divalent aromatic hydrocarbonradical andY is a single bond or a bridging radical in which one or twoatoms separate A³ from A⁴. The free valence bonds in formula III areusually in the meta or para positions of A³ and A⁴ in relation to Y.Compounds in which A² has formula III are bisphenols, and for the sakeof brevity the term “bisphenol” is sometimes used herein to designatethe dihydroxy-substituted aromatic hydrocarbons; it should beunderstood, however, that non-bisphenol compounds of this type may alsobe employed as appropriate.

In formula III, the A³ and A⁴ values may be unsubstituted phenylene orhydrocarbon-substituted derivatives thereof, illustrative substituents(one or more) being alkyl and alkenyl. Unsubstituted phenylene radicalsare preferred. Both A³ and A⁴ are preferably p-phenylene, although bothmay be o- or m-phenylene or one o- or m-phenylene and the otherp-phenylene.

The bridging radical, Y, is a single bond or a radical in which one ortwo atoms, preferably one, separate A³ from A⁴. Illustrative radicals ofthis type include methylene, cyclohexylmethylene,2-[2.2.1]-bicycloheptylmethylene, ethylene, isopropylidene,neopentylidene, cyclohexylidene, cyclopentadecylidene,cyclododecylidene, adamantylidene, O, S, S(O)₂, and C═O. Hydrocarbon andespecially gem-alkylene (alkylidene) radicals are preferred. Alsoincluded, however, are unsaturated radicals. For reasons of availabilityand particular suitability for the purposes of this invention, thepreferred radical of formula III is the 2,2-bis(4-phenylene)propaneradical, which is derived from bisphenol A and in which Y isisopropylidene and A³ and A⁴ are each p-phenylene.

The substituted aromatic compounds of formula I which are employed inthe present invention contain an aromatic radical A¹ and an activatingradical Z. The A¹ radical is normally a di- or polyvalent C₆₋₁₀ radical,preferably monocyclic and preferably free from electron-withdrawingsubstituents other than Z. Unsubstituted C₆ aromatic radicals areespecially preferred.

The Z radical is usually an electron-withdrawing group, which may be di-or polyvalent to correspond with the valence of A¹. Examples of divalentradicals are carbonyl, carbonylbis(arylene), sulfone,bis(arylene)sulfone, benzo-1,2-diazine and azoxy. Thus, the moiety—A¹—Z—A¹— may be a bis(arylene)sulfone, bis(arylene)ketone,tris(arylene)bis(sulfone), tris(arylene)bis(ketone),bis(arylene)benzo-1,2-diazine or bis(arylene)azoxy radical andespecially one in which A¹ is p-phenylene.

Also included are compounds in which —A¹—Z—A¹— is a bisimide radical,illustrated by those of the formulas (IV and (V):

wherein R¹ is a C₆₋₃₀ divalent aromatic hydrocarbon or halogenatedhydrocarbon radical, a C₂₋₂₀ alkylene or cycloalkylene radical, a C₂₋₈bis(alkylene-terminated) polydiorganosiloxane radical or a divalentradical of the formula

in which Q is

or a covalent bond, and n is an integer from 1 to 3 inclusive.Preferably n is 1. Most often, R¹ is at least one of m-phenylene,p-phenylene, 4,4′-oxybis(phenylene) and

Polyvalent Z radicals include those which, with A¹, form part of a fusedring system such as benzimidazole, benzoxazole, quinoxaline orbenzofuran.

Also present in the substituted aromatic compound of formula I are twodisplaceable X¹ radicals which may be fluoro, chloro, bromo or nitro. Inmost instances, fluoro and chloro atoms are preferred by reason of therelative availability and effectiveness of the compounds containingthem.

Among the particularly preferred substituted aromatic compounds offormula I are bis(4-chlorophenyl)sulfone, bis(4-fluorophenyl)ketone and1,3- and 1,4-bis[N-(4-chlorophthalimido)]benzene and4,4′-bis[N-(4-chlorophthalimido)]phenyl ether and the correspondingbromo and nitro compounds. Bis(4-chlorophenyl)sulfone is often mostpreferred.

The second polymer is a condensation polymer characterized by thepresence of an oxycarbonyl group, i.e., —C(O)O—, in its structuralunits. Suitable polymers are polycarbonates and polyarylates. Mostoften, the second polymer is derived from a dihydroxyaromatic compoundhaving formula II. Among polycarbonates, the bisphenol A polycarbonatesare preferred. Polyarylates include bisphenol A iso/terephthalates andthose derived from dihydroxybenzenes, especially resorcinol andhydroquinone iso/terephthalates.

According to the invention, contact is made between the salt, thesubstituted aromatic compound and the second polymer under reactiveconditions, usually parallel to the conditions normally employed forpolyether polymer formation. These may include the presence of a solventand temperatures in the range of about 100-300° C., preferably in therange of about 125-300° C., and more preferably in the range of about150-250° C. Suitable solvents include the dipolar aprotic liquids suchas dimethylformamide, dimethylacetamide, N-methylpyrrolidinone, dimethylsulfoxide and sulfolane, and water-immiscible, relatively non-polararomatic compounds such as chlorobenzene, o-dichlorobenzene and anisoleand mixtures thereof.

When an aromatic solvent is employed, it is strongly preferred for aphase transfer catalyst to be present, especially a phase transfercatalyst with high thermal stability, i.e., one that is stable in therange of about 100-300° C. and preferably in the range of about 125-250°C. Various types of phase transfer catalysts have this property. Theyinclude quaternary phosphonium salts of the type disclosed in U.S. Pat.No. 4,273,712, N-alkyl-4-dialkylaminopyridinium salts of the typedisclosed in U.S. Pat. Nos. 4,460,778 and 4,595,760, and guanidiniumsalts of the type disclosed in the aforementioned U.S. Pat. No.5,229,482. Said patents are incorporated by reference herein. Thepreferred phase transfer catalysts, by reason of their exceptionalstability at high temperatures and their effectiveness to produce highmolecular weight copolymer in high yield, are the hexaalkylguanidiniumand α,ω-bis(pentaalkylguanidinium)alkane salts.

Reagent proportions according to the invention conventionally include a1:1 molar ratio of salt to substituted aromatic compound, althoughslight variations therefrom, up to about 2 mole percent, can betolerated in certain instances. The proportion of second polymer willdepend on the desired proportions of structural units in the productcopolymer. In general, the second polymer will be present in the amountof about 1-80 mole percent and preferably about 2-50 mole percent ofstructural units therein based on substituted aromatic compound.Proportions of catalyst, when employed, are most often in the range ofabout 1-10 mole percent based on substituted aromatic compound.

Although the invention is not dependent upon mechanism, it is believedthat the reaction between the salt and the substituted aromatic compoundin the presence of the second polymer causes extensive reaction of saidpolymer with phenoxide-derived anions, resulting in breakup of thesecond polymer into oligomeric or even monomeric units havingphenoxide-terminated anions as end-groups. These then react with thesubstituted aromatic compound, generally at a significantly slower rate.The product is a copolymer with a more random distribution of ether andcarbonate or ester structural units than is afforded by prior artmethods. It may be isolated from the reaction mixture by conventionaloperations such as anti-solvent precipitation.

Typical weight average molecular weights for the copolymer, asdetermined by gel permeation chromatography relative to polystyrene, arein the range of about 20,000-40,000. It is possible to saponify thecarbonate or ester groups with aqueous alkali and recoverhydroxy-terminated polyether oligomer therefrom; the degree ofpolymerization of said oligomer is typically in the range of about 5-15as determined by hydroxy end-group analysis.

The copolymers of this invention combine the desirable properties of thefirst and second polymers as described herein. Thus, they are useful inapplications requiring combinations of those properties. They can alsobe employed in minor proportions as compatibilizers for blends of saidpolymers, and additionally of blends of said first polymers with, forexample, poly(alkylene carboxylates) such as poly(ethyleneterephthalate) and poly(1,4-butylene terephthalate).

In the second aspect of the invention, the copolymer thus prepared, insolution in the solvent employed, is contacted with an excess, forexample a molar ratio to carbonate and/or ester units within the rangeof about 2-20:1, of aqueous alkali, typically sodium hydroxide orpotassium hydroxide of a concentration in the range of about 0.5-2.5 M,under reactive conditions which most often include temperatures in therange of about 80-150° C. The result is hydrolysis by saponification ofthe carbonate and/or ester groups in the copolymer. What remains ishydroxy-terminated, oligomeric polyether polymer, e.g.,polyethersulfone. Such oligomeric material is not readily prepared innon-polar solvents by other methods, for reasons previously described.It is highly desirable, however, since it can be used as a reagent forpreparation of special purpose copolymers of the types enumeratedhereinabove.

The invention is illustrated by the following examples. All percentagesare by weight. Glass transition temperatures (Tg) were determined bydifferential scanning calorimetry.

EXAMPLE 1

A 300 milliliter (ml), three-necked flask fitted with a stirrer,Dean-Stark trap attached to a condenser and nitrogen purge means wascharged with 9.864 grams (g) (124.17 millimoles [mmol]) of 50.36%aqueous sodium hydroxide solution, 14.172 g (62.08 mmol) of bisphenol A,40 ml of water and 75 ml of toluene. The mixture was heated under refluxand water removed by azeotropic distillation. The majority of thetoluene and about 44 ml of water were distilled off. Then 75 ml ofanisole was added and distillation was continued for one hour.

The Dean-Stark trap was replaced by a recirculating trap filled withcalcium hydride as a drying agent and the mixture was heated underreflux for two hours, with recirculation of the anisole through thecalcium hydride. The resulting slurry of bisphenol A disodium salt wascooled and 17.828 g (62.08 mmol) of bis(4-chlorophenyl)sulfone and 3.947g (15.52 mmol of structural units) of a commercially available bisphenolA polycarbonate were added. The polycarbonate was dissolved by heatingfor 2.5 hours at 95-110° C., after which a solution of 864.2 milligrams(mg) (2.483 mmol) of hexa-n-propylguanidinium chloride in 10 ml of dryanisole was added. The temperature was raised to reflux temperature(152° C.) over two hours, and refluxing was continued for 2.5 hours.

The resulting viscous solution was divided into two approximately equalportions. The first portion was cooled to room temperature, diluted withmethylene chloride and quenched by addition of acetic acid. It was thenmixed with methanol in a blender and the white precipitate was washedwith methanol and twice with hot water and dried in vacuum, yielding thedesired copolyethersulfonecarbonate having a 4:1 ratio of ether sulfoneto carbonate groups, a weight average molecular weight, as determined bygel permeation chromatography relative to polystyrene, of 31,700 and asingle Tg of 177.8° C.

EXAMPLE 2

The second portion of polymer solution from the procedure of Example 1was blended at 100° C. with 6 ml of aqueous potassium hydroxide solutionprepared from 40 mmol of KOH and 25 ml of water, whereupon the viscosityrapidly decreased. After 45 minutes, the mixture was cooled andneutralized with acetic acid. The polyethersulfone oligomer wasprecipitated in methanol, washed with methanol and water and dried. Itsdegree of polymerization, as determined by hydroxy end-group analysis,was 8.64 and its Tg (single) was 117.9° C.

EXAMPLE 3

The procedure of Example 1 was repeated, employing 13.995 g (61.305mmol) of bisphenol A in 75 ml of anisole, 17.604 g (61.305 mmol) ofbis(4-chlorophenyl)sulfone, 1.732 g (6.182 mmol of structural units) ofbisphenol A polycarbonate and 853 mg (2.45 mmol) ofhexa-n-propylguanidinium chloride. The polymerization mixture was heatedunder reflux for 1.5 hours and divided into two approximately equalportions. The product copolymer obtained from the first portion had aweight average molecular weight of 28,740 and a single Tg of 179.7° C.

EXAMPLE 4

The second portion of the reaction mixture of Example 3 was contactedwith aqueous potassium hydroxide mixture as described in Example 2. Thepolyethersulfone oligomer thus recovered had a degree of polymerizationof 11.42 and a Tg of 154.9° C.

EXAMPLE 5

As a control experiment a polymerization was conducted in the absence ofthe second polymer (polycarbonate) and by use of excess amount ofbisphenol A salt relative to bis(4-chlorophenyl)sulfone with intent ofobtaining polyethersulfone oligomer. Thus anhydrous disodium salt wasprepared from 13.018 g (57.03 mmol; 10% molar excess) of bisphenol A in75 ml of anisole. Polymerization was performed employing 14.738 g (51.32mmol) of bis(4-chlorophenyl)sulfone and 794 mg (2.28 mmol) ofhexa-n-propylguanidinium chloride. The polymerization mixture was heatedunder reflux for 0.5 hours and the product was isolated. Thepolyethersulfone had a weight average molecular weight of 41,700 despite10% excess of bisphenol A salt being employed. The theoretical weightaverage molecular weight, if the reaction were run in a homogeneoussystem, was expected to be about 8,200 (degree of polymerization about10).

EXAMPLE 6

The procedure of Example 1 was repeated, employing 4.555 g (113.87 mmol)of 50.36% aqueous sodium hydroxide, 12.997 g (56.93 mmol) of bisphenolA, 16.349 g (56.93 mmol) of bis(4-chlorophenyl)sulfone, 792 mg (2.28mmol) of hexa-n-propylguanidinium chloride along with 90 ml of anisole,and substituting 1.520 g (6.33 mmol polymer repeat unit) of apolyarylate (Mw=105,000) derived from resorcinol and 1:1iso/terephthalate for the polycarbonate. A copolyesterethersulfone wasobtained having a single Tg of 172° C. and weight average molecularweight of 25,600.

EXAMPLE 7

The procedure of Example 1 was repeated, substituting1,3-bis[N-(4-chlorophthalimido)]benzene for thebis(4-chlorophenyl)sulfone on an equimolar basis to the polycarbonate(i.e. 15.52 mmol). A copolyetherimidecarbonate was obtained with asingle Tg of 204° C. and weight average molecular weight of 40,000.

EXAMPLE 8

The procedure of Example 1 is repeated, substitutingbis(4-fluorophenyl)ketone on an equimolar basis for thebis(4-chlorophenyl)sulfone. A copolyetherketonecarbonate is obtained.

While typical embodiments have been set forth for the purpose ofillustration, the foregoing descriptions should not be deemed to be alimitation on the scope of the invention. Accordingly, variousmodifications, adaptations, and alternatives may occur to one skilled inthe art without departing from the spirit and scope of the presentinvention.

What is claimed is:
 1. A method for preparing a copolymer of a firstpolymer which is a polyethersulfone and a second condensation polymerwhich is a polyarylate, which comprises contacting, under reactiveconditions, at least one salt of a dihydroxyaromatic compound with atleast one substituted aromatic compound of the formula Z(A¹—X¹)₂,  (I)wherein Z is an activating radical, A¹ is an aromatic radical and X¹ isfluoro, chloro, bromo or nitro, in the presence of said second polymer.2. The method according to claim 1 wherein the second polymer is presentin the amount of about 2-50 mole percent of structural units thereinbased on substituted aromatic compound.
 3. The method according to claim2 wherein the molar ratio of said salt to said substituted aromaticcompound is 0.98-1.02:1.
 4. The method according to claim 2 wherein thecontact temperature is in the range of about 125-300° C.
 5. The methodaccording to claim 2 wherein the dihydroxyaromatic compound salt is asodium or potassium salt.
 6. The method according to claim 2 wherein asolvent is present.
 7. The method according to claim 6 wherein thesolvent is a dipolar aprotic solvent.
 8. The method according to claim 6wherein the solvent is a water-immiscible aromatic compound.
 9. Themethod according to claim 8 wherein the solvent is o-dichlorobenzene oranisole or a mixture thereof.
 10. The method according to claim 8wherein a phase transfer catalyst is also present.
 11. The methodaccording to claim 10 wherein the phase transfer catalyst is ahexaalkylguanidinium halide.
 12. The method according to claim 10wherein the contact temperature is in the range of about 125-250° C. 13.The method according to claim 3 wherein the molar ratio of said salt tosaid substituted aromatic compound is 1:1.
 14. The method according toclaim 1 wherein the polyarylate is a bisphenol A, resorcinol orhydroquinone iso/terephthalate.
 15. The method according to claim 2wherein the substituted aromatic compound is a bis(haloaryl)sulfone. 16.The method according to claim 15 wherein the bis(haloaryl)sulfone isbis(4-chlorophenyl)sulfone.
 17. A method for preparing a copolymer of apolyethersulfone and a polyarylate which comprises contacting, underreactive conditions, at least one alkali metal salt of bisphenol A withbis(4-chlorophenyl)sulfone in solution in o-dichlorobenzene or anisole,in the presence of a polyarylate and about 1-10 mole percent, based onsaid bis(4-chlorophenyl)sulfone, of a hexaalkylguanidinium halide asphase transfer catalyst and at a temperature in the range of about125-250° C.